Novak Djokovic launched his campaign for a second French Open title with a moody victory over Brazilian qualifier Rogerio Dutra Silva on Monday, winning 6-3, 6-4, 6-4.

In his quest to become the first men's player in the Open era to win each of the Grand Slams twice, Djokovic, who underwent surgery on his elbow after January's Australian Open, looked unhappy even when he was stroking winners past his opponent.

"You don't always get to feel your best but all you can do is try and get the best out of it," the Serbian told a packed Philippe Chatrier court.

Djokovic, who didn't play a competitive match between Wimbledon last July and Melbourne, endured a tough run into Roland Garros. He fell in the second rounds at Barcelona and Madrid before reaching the semi-finals in Rome, where he was defeated by world number one Rafael Nadal.

Djokovic has never lost to a player ranked as low as Dutra Silva at number 134, but the claycourt specialist pushed his opponent around the court drawing frequent outbursts of frustration from the Serb.

"He's a fighter. It was a good test for the first match," Djokovic told a news conference.

The 2016 Roland Garros champion said he felt he was beginning to play better and free of pain after "a long 12 months". This year is the first that Djokovic has not won a tour-level title prior to the French Open.

Two-time Grand Slam winner Victoria Azarenka crashed out of the French Open in the first round losing 5-7, 5-7 to Katerina Siniakova on Monday, playing only her fifth tournament of the year after a legal battle over the custody of her son.

The Belarusian returned to tennis in June last year following the birth of her son in 2016 but then put her career on hold again as she fought a legal battle against her former partner. A judge in California had ruled that her son Leo should not leave the state until custody was resolved.

After losing the first set, Azarenka showed signs of a comeback, winning a fierce-hitting baseline exchange to go to 2-2. But she was unable to build momentum even as her Czech opponent lost her cool over a handful of disputed line calls.

Former world number one Azarenka has endured a tough return to Europe's clay courts, losing in the second round at the Madrid Open before being dumped out of the first round in Rome. She is currently ranked 84 in the world.

The months-long custody fight over her son Leo has been a painful distraction for Azarenka, and the 28-year-old said she had been looking forward to her return to Paris.

"Ah Paris, we love each other, no?," She tweeted earlier this month.

In an open letter posted on social media last year, Azarenka said no one should ever have to decide between a child and their career.

Azarenka won the Australian Open in 2012 and 2013. Her best performance at Roland Garros was in 2013 when she lost in the semi-finals to Russia's Maria Sharapova. She has said she will play at Wimbledon this year.

Petra Kvitova came within three points of falling in the first round of the French Open before three successive aces and her nerves of steel carried her to a 3-6, 6-1, 7-5 win over little-known Paraguayan Veronica Cepede Royg on Monday.

The Czech, who suffered career-threatening injuries on her playing left hand after being attacked in her home by a knife-wielding intruder in December 2016, arrived in Paris on the back of an 11-match winning streak.

But Cepede Royg came close to snapping that run as she edged 5-4 and 0-15 ahead on Kvitova's serve in the third set.

But the woman who proved even her surgeon wrong by coming back to play top left tennis just five months after the attack unleashed three successive aces to survive that scare.

She was soon saluting the crowd with a raised clenched-fist as she broke in the next game before wrapping up victory to set up a second-round meeting with Spain's Lara Arruabarrena.

The most recently minted Grand Slam champion in tennis booked her second round French Open slot on Monday as Caroline Wozniacki overcame a stuttering start to beat Danielle Collins 7-6(2) 6-1 in Paris.

The Dane, who landed her first major at the Australian Open earlier this year in what was her 43rd Grand Slam attempt, generally prefers faster surfaces, but looked increasingly at ease once she had ironed out some early glitches.

Collins, coming into this tournament on a career-high ranking of 42, fought throughout but was unable to hold off Wozniacki who won on a bizarre point after the umpire ruled a Collins shot had been long while the American, her back turned, was preparing to play on.

Seeded two here, Wozniacki is one of six players who could end the tournament world number one.

Kristina Mladenovic's crawl back to her best level stopped in abrupt fashion on Monday as she suffered a remarkable meltdown in a 7-6(10), 6-2 defeat by a resurgent Andrea Petkovic in the first round of the French Open.

The Frenchwoman, who had slipped down the rankings after 15 consecutive defeats between the end of July and mid-January, seemed on her way up again thanks to some recent landmark wins.

It appeared that a year after reaching the quarter-finals, she could make light work of German Petkovic, a former semi-finalist at Roland Garros. However, two consecutive double faults as she had three set points in the opening set's tiebreak threw her off balance.

Mladenovic, who recently beat former French Open finalist Sam Stosur, never recovered and allowed world number 107 Petkovic to claim only her third victory on the main tour this year -- also her fifth in as many encounters between the two.

Mladenovic started confidently on the Suzanne Lenglen court, where last year she beat then defending champion Garbine Muguruza to reach the last eight, opening up a 2-0 lead.

But Petkovic broke back and forced a tiebreak, in which the Frenchwoman, seeded 29th, went 6-3 ahead.

The mercury rose in the stadium with the crowd chanting 'Kiki, Kiki!' to support a player who set their hearts on fire last year.

Mladenovic, however, collapsed, serving two consecutive double faults on set points and eventually losing the tiebreak 12-10 as she netted a forehand.